Classifications

• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
  • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
  • C12Q1/001—Enzyme electrodes
  • C12Q1/002—Electrode membranes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S435/00—Chemistry: molecular biology and microbiology
  • Y10S435/817—Enzyme or microbe electrode

Definitions

• This invention relates to sensor devices such as are used in the determination of a component or components which may be present in a fluid sample, such as a physiological fluid (e.g. blood) or other fluids of biological origin (e.g. fruit), process fluids or effluents.
• a fluid sample such as a physiological fluid (e.g. blood) or other fluids of biological origin (e.g. fruit), process fluids or effluents.
• Some forms of sensor rely on the components used to make the membrane, while others rely on the mode of fabrication of the membrane, selecting its physical properties (for example its porosity) or treatments given to it, as these factors can control its effectiveness and selectivity in use.
• sensors incorporate an enzyme, which converts one substrate compound or analyte into another which may then be more easily measured.
• an enzyme which converts one substrate compound or analyte into another which may then be more easily measured.
• oxidase enzymes which generate hydrogen peroxide--a substance which can be measured very conveniently and very accurately by electrolytic methods, especially amperometrically.
• European Patent No. 216577 (of ICI PLC) which specifies an enzyme electrode sensor with membrane barrier of low (>5%) porosity.
• Such known sensors utilising various membrane materials, are very valuable in analytical techniques and the analysis of biological fluids (e.g. blood) for the presence of substances considered critical for medical reasons--e.g. glucose and other materials which may be oxidizable or reducable, or have toxic properties.
• an improved sensor device comprising means for detecting components present in fluid samples and providing an output representative of the content of said component comprising a detecting means and a membrane barrier between the detecting means and the sample to be analyzed, characterised in that the membrane barrier is composed of polyvinyl chloride (PVC) itself, in un-plasticized form.
• PVC polyvinyl chloride
• the detecting means is most conveniently of one of an electrochemical nature, but other types (e.g. spectrophotometric or optical detecting systems) may be used if desired.
• the detecting means will usually comprise an electrode system and a liquid or gel phase electrolyte-containing medium.
• the electrolyte will be aqueous (i.e. aqueous or aqueous-based) but the use of non-aqueous electrolyte media (for example organic-based media) is not excluded.
• the sensor device comprises a detecting means in contact with an electrolyte medium and both associated with a membrane of polyvinyl chloride (PVC) itself, in un-plasticized form, which provides an interface for contact with a sample to be analyzed and interposed between the active electrode (anode) of the cell used as detector.
• PVC polyvinyl chloride
• Alternative forms of construction may have both the electrodes of the detecting means (cell) enclosed within the PVC membrane (so that both are separated from the sample) or (b) only the anode of the detecting means (cell) enclosed within the PVC membrane (so that the PVC membrane is between the electrodes and the cathode is not separated from the sample).
• the former is very convenient and compact, but the latter is more simple and is made practicable by the fact that PVC in un-plasticized form is less insulating in its properties, and H + ions can pass through it.
• the sensor device of our invention can have a single membrane or, if desired, multiple layers of membrane material. When multiple layers of membrane are used, these may be the same or different.
• the preference for the position to be occupied by the un-plasticized PVC membrane differs to some degree according to the particular use to which the sensor is being applied and what substrate compound is to be detected by the sensor.
• the governing factor is mainly the fact that un-plasticized PVC is permeable to hydrogen peroxide and some low molecular weight species (for example oxalate) but impermeable to some sugars, and permeable to others for example glucose.
• a sensor assembly is best made with an enzyme (with which the desired substrate can interact and generate a species which can pass through the un-plasticized PVC) situated outside the un-plasticized PVC membrane, so that the desired species in the sample under examination can make contact with the enzyme--either directly or indirectly, through another selective membrane layer--and thereby generate a species to which the un-plasticized PVC membrane is permeable.
• an oxidase enzyme can be used and the hydrogen peroxide thus generated can pass through the un-plasticized membrane and be determined at the detector means.
• any membrane layer or layers other than any comprised of un-plasticized PVC may be made of any of the wide variety of materials known in the art. Examples of these include dialysis membranes, and in general are preferably non-diffusion limiting membranes, at least to the extent that they do not limit diffusion and passage of desired species towards the detecting means.
• un-plasticized PVC is used as in inner membrane (i.e. a layer which is not the outermost)
• one or more outer layers may be used which are of material which protects the sensor assembly in a mechanical manner (e.g. from mechanical damage) or in a chemical or any other manner considered appropriate for the use to which it is to be applied.
• an outer layer comprising a polycarbonate (especially in a porous form).
• the active electrode may be any of those known in the art, for example a metal electrode, but especially a platinum anode. This is most conveniently made in combination with a silver/silver chloride counter electrode, as for example in the so-called Clark electrode, which comprises a platinum electrode surrounded by a silver/silver chloride ring.
• the PVC polyvinyl chloride
• the PVC may, be any polymer of vinyl chloride, as for example those made and available commercially, but should be free from any added plasticizer (an ingredient which is often present in some commercial products intended for uses such as molding).
• plasticizer an ingredient which is often present in some commercial products intended for uses such as molding.
• Such "un-plasticized" PVC polymers are readily obtainable in commerce, however, and it is necessary only for the quality and purity of any polymer to be checked, whether by its specification or labelling.
• the molecular weight of the PVC is relatively non-critical, and most commercial grades will be satisfactory in use. A typical molecular weight is in the range 10,000 to 200,000, but others may be used if desired.
• the material i.e. the un-plasticized polyvinyl chloride
• the material may be made into membranes by any conventional method. Most conveniently, this can be done by solution casting techniques, using solvents to dissolve the polymer and then spreading the solution on a plate or flat surface and allowing the solvent to evaporate.
• a convenient solvent is tetrahydrofuran (THF), but other solvents or mixtures of solvents which are known to be able to dissolve PVC be used if desired.
• the thickness of the membranes can be of the order already used conventionally in the art, but my be varied as found most appropriate having regard for the particular mixed polymer composition being used and the conditions under which it is to be used. Thus a convenient thickness is in the range 10 to 40 ⁇ m, though larger or smaller thicknesses can be used if desired.
• the un-plasticized PVC is the outer membrane, and in the other it is the inner membrane.
• the components are mainly the conventional ones, and the many variants known in the art may be used.
• Un-plasticized PVC is not sufficiently permeable to glucose, so direct electrochemical detection of glucose cannot be achieved through this material as membrane. However, it is permeable to hydrogen peroxide, so enabling an alternative glucose-permeable membrane and an oxidase enzyme to be used to produce hydrogen peroxide, which then can selectively permeate the un-plasticized PVC membrane.
• This un-plasticized PVC membrane has a particular advantage over plasticized PVC in that it is (unlike the plasticized form) impermeable to paracetamol--so that this compound is excluded from interfering with hydrogen peroxide detection, as well as ascorbate/urate.
• This selectivity against paracetamol and the like while in favor of hydrogen peroxide is a valuable property which is not easily found and it very useful in clinical and related analytical, diagnostic and monitoring work.
• any other sensor device or system using an oxidase enzyme to generate hydrogen peroxide can, with advantage, incorporate an un-plasticized PVC membrane as part of its construction, especially as an inner membrane near to the active electrode surface.
• sensor devices of the electrolytic (amperometric) type are often used for examination of biological fluids for example blood, urine, and the like. It happens that urine contains a number of interferents which--even though their identity has not yet been established--have the ability to permeate many of the known conventional membrane materials, for example plasticized PVC, and so interfere severely with the accurate estimation of components such as hydrogen peroxide and of compounds which can be used to generate it.
• the un-plasticized form of PVC does not allow these unidentified components to pass through, is it constitutes an effective barrier to them and facilitates the wider applicability and accuracy of measurement. Thus, for many applications the un-plasticized PVC membrane will be preferable, though it will not always be so in applications in which it is desired to have a phenolic compound permeating the membrane.
• un-plasticized PVC membrane is used in the construction of a sensor device for the determination of oxalate. It acts in this in two ways, both of which are valuable.
• One is a form of sensor in which the un-plasticized PVC membrane is used as an inner membrane beneath a layer or membrane comprising an oxalate oxidase system, so that hydrogen peroxide is generated from the sample and the resulting hydrogen peroxide passes through the un-plasticized PVC membrane; this relies on its action as a membrane selectively permeable to hydrogen peroxide.
• the un-plasticized PVC membrane can be used as an outer layer with the means for oxalate detection beneath it; this relies on its unexpected ability to act as a membrane selectively permeable to oxalate.
• Un-plasticized PVC is the only material that we know of at present which is oxalate-selective, and the mechanism by which it performs in this way is still not clear to us.
• the means for detecting the oxalate which has passed through the un-plasticized PVC membrane may be any of those known and may be either an enzyme one (oxalate oxidase based) or one which detects and measures the oxalate directly by electrolytic action. This may be amperometric, and the pH of the medium around the active electrode may be adjusted as may be found most appropriate by simple trial.
• oxalate or oxalic acid from sample (1) passes through the un-plasticized PVC membrane (2) and then, by contact with the enzyme (3), generates hydrogen peroxide and carbon dioxide.
• the hydrogen peroxide then passes through the inner membrane (4) to the electrode (5), at which it is determined electrolytically.
• the inner membrane (4) may be of any convenient material--for example a dialysis membrane or a polycarbonate membrane--intended to perform such actions as regulation of the flow of components to electrode (5) (should this be considered desirable) or to provide mechanical protection and add to the robustness of the sensor assembly and minimize risk of damage to the innermost electrode elements.
• membranes comprising un-plasticized polyvinyl chloride.
• these in the form of multi-layer membrane products in which at least one layer is formed of un-plasticized polyvinyl chloride and is combined with one or more layers of other materials of appropriate properties to enhance the properties of the un-plasticized polyvinyl chloride itself.
• Such materials may be of appropriate permeability to regulate the access of components before or after passage through the un-plasticized polyvinyl chloride, and/or of a physical form or strength which protects the un-plasticized polyvinyl chloride from damage or provides it with any desired degree of stability of shape or positioning in use.
• membranes of un-plasticized polyvinyl chloride incorporating an enzyme for example an oxidase.
• the enzyme may be immobilized by the chemical means known in the art, or they may be held between the layers of a multi-layer structure.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Wood Science & Technology (AREA)
• Proteomics, Peptides & Aminoacids (AREA)
• Zoology (AREA)
• Engineering & Computer Science (AREA)
• Immunology (AREA)
• General Engineering & Computer Science (AREA)
• Microbiology (AREA)
• Molecular Biology (AREA)
• Analytical Chemistry (AREA)
• Biotechnology (AREA)
• Physics & Mathematics (AREA)
• Biochemistry (AREA)
• Bioinformatics & Cheminformatics (AREA)
• Biophysics (AREA)
• General Health & Medical Sciences (AREA)
• Genetics & Genomics (AREA)
• Measuring Or Testing Involving Enzymes Or Micro-Organisms (AREA)
• Investigating Or Analysing Biological Materials (AREA)
• Push-Button Switches (AREA)
• Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)
• Measuring Fluid Pressure (AREA)
• Apparatus Associated With Microorganisms And Enzymes (AREA)

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Citations (7)

• 1992
  • 1992-07-28 GB GB929215973A patent/GB9215973D0/en active Pending
• 1993
  • 1993-07-23 DE DE69304922T patent/DE69304922T2/de not_active Expired - Fee Related
  • 1993-07-23 US US08/374,740 patent/US5567290A/en not_active Expired - Fee Related
  • 1993-07-23 WO PCT/GB1993/001566 patent/WO1994002585A1/en active IP Right Grant
  • 1993-07-23 EP EP93917908A patent/EP0652942B1/en not_active Expired - Lifetime
  • 1993-07-23 CA CA002140436A patent/CA2140436A1/en not_active Abandoned
  • 1993-07-23 AU AU47159/93A patent/AU4715993A/en not_active Abandoned
  • 1993-07-23 AT AT93917908T patent/ATE143051T1/de not_active IP Right Cessation
  • 1993-07-23 DK DK93917908.1T patent/DK0652942T3/da active
  • 1993-07-23 ES ES93917908T patent/ES2093449T3/es not_active Expired - Lifetime
  • 1993-07-23 JP JP6504314A patent/JPH08502349A/ja active Pending
• 1996
  • 1996-12-16 GR GR960403481T patent/GR3022049T3/el unknown

Patent Citations (7)

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